1. Field of the Invention
The present invention relates to a light source device equipped with a discharge lamp that has a pair of electrodes, the driving method of such a discharge lamp, and a projector that incorporates such a discharge lamp.
2. Description of the Related Art
As a lighting method for a high intensity discharge lamp, U.S. Pat. No. 6,815,907 discloses to supply alternating lump current to a high intensity discharge lamp. In the disclosure, absolute value of the alternating lump current is roughly fixed, and the pulse width modulation of the alternating lamp current is performed. Specifically, it is disclosed to set lighting frequency to 40 Hz to 5 kHz, and to modulate the pulse width ratio of the positive pulse and negative pulse with a sine wave of 0.1 Hz to 100 Hz (specifically, 50 Hz) which is lower than the lighting frequency.
However, even when modulating the pulse width of an alternating lamp current as disclosed in U.S. Pat. No. 6,815,907, when the pulse width modulation frequency is high, a steady convection flow is formed at the inside of the high intensity discharge lamp, and biased consumption of the electrode and biased precipitation of the electrode materials may occur.